Optical bistability and lasing of crystals containing impurities in the case of an adiabatic electron–phonon interaction

A theoretical study is made of the threshold conditions for the observation of optical bistability and stimulated emission of zero-phonon lines of crystals containing impurities. A reduction in the electron–photon interaction constant ensures that nonlinear absorption due to a purely electronic transition is attained in a lower saturating field and the lasing threshold rises exponentially as the reciprocal of the Debye–Waller factor. It is shown that there are critical temperatures for the appearance of these effects. Experimental studies of the threshold conditions for lasing and optical bistability make it possible to determine directly the Debye–Waller factor at different temperatures of a crystal.